Solid-state imaging device and camera

Abstract

Specifically, the solid-state imaging device includes: pixels each of which includes an amplifying transistor that amplifies a signal; first column signal lines each of which is connected to one of the columns of the pixels; first load transistors each of which is connected to one of the first column signal lines; a bias circuit which supplies a bias voltage to a gate of each of the first load transistors; first detection units each of which is connected to the one of the first column signal lines; a second detection unit which detects a noise component of each of the rows, the noise component occurring in each of the first column signal lines and resulting from fluctuation in the bias voltage; and a correction unit which corrects, the pixel signal detected by each of the first detection units, using the noise component detected by the second detection unit.

1 . A solid-state imaging device comprising:
 pixels which are arranged in rows and columns, and each of which includes an amplifying transistor that amplifies a signal;   first column signal lines each of which is connected to one of the columns of said pixels, and through each of which the signal amplified by said amplifying transistor is transmitted;   first load transistors each of which is connected to one of said first column signal lines;   a bias circuit which supplies, through a bias signal line, a bias voltage to a gate of each of said first load transistors;   first detection units each of which is connected to the one of said first column signal lines, and each configured to detect a pixel signal from the signal transmitted through the one of said first column signal lines;   a second detection unit configured to detect a noise component of each of the rows, the noise component occurring in each of said first column signal lines and resulting from fluctuation in the bias voltage; and   a correction unit configured to correct, for each of the rows, the pixel signal detected by each of said first detection units, using the noise component detected by said second detection unit.   
     
     
         2 . The solid-state imaging device according to  claim 1 ,
 wherein said second detection unit includes:   a reference voltage generating unit arranged in a row, including a reference voltage generating transistor, and configured to generate a reference voltage signal;   a second column signal line which is connected to said reference voltage generating unit, and through which the reference voltage signal generated by said reference voltage generating unit is transmitted;   a second load transistor which is connected to said second column signal line, and has a gate connected to the bias signal line; and   a fluctuation detection unit connected to said second column signal line, and configured to detect the noise component occurring in the reference voltage signal transmitted through said second column signal line,   wherein said correction unit is configured to correct the pixel signal detected by each of said first detection units, using the noise component detected by said fluctuation detection unit included in said second detection unit.   
     
     
         3 . The solid-state imaging device according to  claim 2 ,
 wherein said first detection units each are configured to detect the pixel signal by performing correlated double sampling on the signal transmitted through the one of said first column signal lines, and   said fluctuation detection unit is configured to detect the noise component by performing the correlated double sampling on the reference voltage signal with same timing as each of said first detection units.   
     
     
         4 . The solid-state imaging device according to  claim 1 ,
 wherein said second detection unit includes reference voltage generating units including said reference voltage generating unit, and   said correction unit includes:   an averaging circuit which calculates an average noise signal by averaging detected noise components; and   a subtracting circuit which corrects the pixel signal of each of the columns which is detected for each of the rows, by subtracting the average noise signal from the pixel signal.   
     
     
         5 . The solid-state imaging device according to  claim 4 ,
 wherein, while pixel signals of each of the rows are detected, said correction unit is configured to hold the average noise signal of a corresponding one of the rows, and   said subtracting circuit corrects the pixel signal of each of the columns which is detected for each of the rows, by subtracting the held average noise signal from the pixel signal.   
     
     
         6 . The solid-state imaging device according to  claim 3 ,
 wherein said first detection units each include a first AD conversion circuit which detects the pixel signal by converting the signal into a first digital signal and performing the correlated double sampling on the first digital signal, the signal being transmitted through the one of said first column signal lines, and   said fluctuation detection unit includes a second AD conversion circuit which detects the noise component by converting the reference voltage signal into a second digital signal and performing the correlated double sampling on the second digital signal, the reference voltage signal being transmitted through said second column signal line.   
     
     
         7 . The solid-state imaging device according to  claim 4 ,
 wherein said correction unit further includes a signal level limiting circuit which removes, from the noise component, either a component equal to or higher than a first threshold value or a component equal to or lower than a second threshold value, before said averaging circuit calculates average noise signals of each of the rows, and   said averaging circuit calculates the average noise signals of each of the rows, using the noise component from which either the component equal to or higher than the first threshold value or the component equal to or lower than the second threshold value is removed.   
     
     
         8 . The solid-state imaging device according to  claim 1 ,
 wherein a product of a gate width and a gate length of a reference voltage generating transistor is larger than a product of a gate width and a gate length of said amplifying transistor.   
     
     
         9 . The solid-state imaging device according to  claim 8 ,
 wherein said correction unit is configured to multiply a calculated average noise signal by a predetermined coefficient determined according to a ratio of a transconductance value of said amplifying transistor to a transconductance value of the reference voltage generating transistor, and   said correction unit includes a subtracting circuit which corrects the pixel signal of each of the columns which is detected for each of the rows, by subtracting the average noise signal multiplied by the predetermined coefficient from the pixel signal.   
     
     
         10 . The solid-state imaging device according to  claim 1 ,
 wherein a ratio of a gate width of a reference voltage generating transistor to a gate length of the same is equal to a ratio of a gate width of said amplifying transistor to a gate length of the same.   
     
     
         11 . The solid-state imaging device according to  claim 1 ,
 wherein a transconductance value of a reference voltage generating transistor is equal to a transconductance value of said amplifying transistor.   
     
     
         12 . The solid-state imaging device according to  claim 1 ,
 wherein said pixels, said first column signal lines, said first load transistors, said bias circuit, said first detection units, and said second detection unit are included in a same LSI chip, and   said correction unit is externally attached to the LSI chip.   
     
     
         13 . A camera comprising the solid-state imaging device according to  claim 1 .